package com.stillcoolme.sql.orgexample.streaming;


import org.apache.spark.api.java.function.FlatMapFunction;
import org.apache.spark.sql.*;
import org.apache.spark.sql.streaming.StreamingQuery;

import java.util.Arrays;
import java.util.Iterator;

/**
 * Counts words in UTF8 encoded, '\n' delimited text received from the network.
 *
 * Usage: JavaStructuredNetworkWordCount <hostname> <port>
 * <hostname> and <port> describe the TCP server that Structured Streaming
 * would connect to receive data.
 *
 * To run this on your local machine, you need to first run a Netcat server
 *    `$ nc -lk 9999`
 * and then run the example
 *    `$ bin/run-example sql.streaming.JavaStructuredNetworkWordCount
 *    localhost 9999`
 */
public final class JavaStructuredNetworkWordCount {

    public static void main(String[] args) throws Exception {
        if (args.length < 2) {
            System.err.println("Usage: JavaStructuredNetworkWordCount <hostname> <port>");
            System.exit(1);
        }

        String host = args[0];
        int port = Integer.parseInt(args[1]);

        SparkSession spark = SparkSession
                .builder()
                .appName("JavaStructuredNetworkWordCount")
                .master("local")
                .getOrCreate();

        // Create DataFrame representing the stream of input lines from connection to host:port
        Dataset<Row> lines = spark
                .readStream()
                .format("socket")
                .option("host", host)
                .option("port", port)
                .load();

        // Split the lines into words
        Dataset<String> words = lines.as(Encoders.STRING())
                .flatMap(new FlatMapFunction<String, String>() {
                    @Override
                    public Iterator<String> call(String x) {
                        return Arrays.asList(x.split(" ")).iterator();
                    }
                }, Encoders.STRING());

        // Generate running word count
        Dataset<Row> wordCounts = words.groupBy("value").count();

        // Start running the query that prints the running counts to the console
        StreamingQuery query = wordCounts.writeStream()
                .outputMode("complete")
                .format("console")
                .start();

        query.awaitTermination();
    }
}

